Gyraf Audio G9 Micpre Tubes

[gct]

HI

I was planning to build the G9 stereo mic preamp.  Has anyone had experience with the G9?

The G9 specifies 4x ECC82 valves, 2 for each channel. I have some other valves. Can any of these be used in the G9?

2x Philips EL84
2x Philips ECC83
1x Valvo EZ80

Cheers

GCT

 

[braeden]

I'm not a tube expert, but you would most likely have to modify the circuit, I don't think the voltages are the same for those other types of tubes.
The G9 only really specifies a 12AU7/ECC82 type tube, is there any reason why you'd want to change? I am in the process of building a G9 as well and I have heard a lot of great things about the stock standard G9 build with no mods.

 

[Nele]

The G9 specifies 4x ECC82 valves, 2 for each channel. I have some other valves. Can any of these be used in the G9?

2x Philips EL84
2x Philips ECC83
1x Valvo EZ80

No, you can't use these. EL84 is end-stage powertube, ECC83 is preamp-tube with different specs, ez80 is rectifier tube.

 

[gct]

Thanks for the quick response.
Cheers

GCT

 

[gemini86]

Sounds like you have a good setup for a valve jr though.

Ecc82 is also 12au7, very easy to find tube.

 

[gct]

Just got a tube mic TBone SCT800/Apex460 with a Chinese  12AX7B

Is the ECC83 a suitable replacement or will I damage something? (I have one already)

Cheers

GCT

 

[Majestic12]

12AX7 = ECC83

same tube, different name...it definately will work

 

[gct]

That's good news.Thanks
GCT

 

[telefunk]

Rather try ECC81/12AT7, i'll have bit less gain but will probably sound smoother.

 

[gemini86]

Rather try ECC81/12AT7, i'll have bit less gain but will probably sound smoother.

agreed...

the ax7 is just so much gain, on most sources you're going to end up padding it, or turning your pre down. I like the at7 myself...

eccXX is the European designations for tubes. E meaning 6-7V heater, CC meaning dual triode, then 81 being the specific model.

So using that you can learn that ef86, is not a triode, but a small signal pentode(f) with a 6-7V heater (6.3V to be precise). EL84 is a power pentode(L meaning power pentode) with a 6.3V heater.

etc...etc... This works pretty well to get sift through a box of old tubes to find ones that may be of use to you....but a glace at the datasheet is a must before using it, as we Americans sucked at sticking to a convention. 6au7 was a 6V heater version of 12au7, but the 25L6 was NOT the same tube as a 6L6... So be careful.

 

[gct]

Thanks again. I am looking for background  info so I can understand the basics of tube circuits. Where can I find an explaination of how the circuits work? Like cathode follower, bias circuit, etc

 

[gemini86]

http://valvewizard.co.uk/

 

[telefunk]

This place is full of explanations about Apex 460/Nady 1150 etc...

There is a PDF about Apex 460 mods going around in Slutz, check the schematics and you'll get it. These mods have the CF removed, meaning the other half of the tube is turned off, grounded.

http://www.gearslutz.com/board/attachments/geekslutz-forum/111879d1235602544-apex-460-mod-u47-apex-460-mods.pdf

 

[gct]

Just changed the valve and removed the RF caps. BIG difference - my first mod so I'm really pleased.

Many thanks - will get reading up on the next steps.

GCT